Burner shut off

ABSTRACT

A burner shutoff for a burner, the burner shutoff including a solenoid moveable between an open position permitting fuel supply to the burner and a closed position cutting off fuel supply to the burner. The burner shutoff including a thermocouple in communication with the solenoid, wherein the thermocouple producing a voltage output signal when heated by the burner for maintaining the solenoid in the open position. The burner including a safety timer for selectively generating and communicating a reverse polarity voltage signal to the solenoid such that the voltage signal received by the solenoid is altered sufficiently to move the solenoid to the closed position, thereby shutting off the burner.

FIELD OF THE INVENTION

The present invention generally relates to a safety automatic shut off device for gas burners.

BACKGROUND OF THE INVENTION

Heaters often utilize gas fired burners which normally operate with propane fuel, however can also have other sources of fuel, including but not limited to natural gas, butane and heating oil. Most portable heaters having gas fired burners are fitted with a safety thermocouple which communicates electrically with a solenoid valve in order to detect a flame out condition. The thermocouple mounted proximate the flame or heat source develops a millivolt signal which in turn is communicated back to the solenoid valve. The millivolt signal maintains the solenoid valve in the open position. When a flame out condition occurs, the thermocouple cools downs and the millivolt signal decreases which in turn closes off the solenoid valve once the signal from the thermocouple has dropped to a certain predetermined level.

Small heaters having gas fired burners are often used in very small enclosed spaces and under the right conditions, the gas fired burners may deplete the amount of oxygen within the enclosed space and under certain conditions may give off carbon monoxide which can be hazardous to the occupant of the enclosed space.

Therefore it is desirable to have a safety device and/or a safety feature which will prevent or minimize the possibility of oxygen depletion within small enclosed spaces and/or the development of carbon monoxide in order to prevent hazardous conditions from forming within small enclosed spaces in which the heaters are located.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments now be described by way of example only with reference to the following diagrams in which:

FIG. 1 is a schematic diagram of the burner shut off as shown deployed with a heater.

FIG. 2 is a schematic wiring diagram of the burner shut off showing details of the wiring of the safety timer.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present embodiment of burner shut off is shown generally as 100 in FIGS. 1 and 2. In FIG. 1, burner shut off 100 is shown deployed together with a heater 102. In one example heater 102 is a portable space heater of the type having a high intensity ceramic type gas burner. Burner shut off 100 may also be applicable to other heaters.

Burner shut off 100 includes safety timer 202 which includes circuit board 214 having the following major components, namely a timer 204, a micro processor 206, a power storage device 208 and a power supply preferably a battery 212.

The burner shut off 100 further includes a thermocouple 220 having thermocouple wires 222 in electrical communication with solenoid valve 230 which also has a manual push button 232.

Safety timer 202 is in electrical communication with thermocouple wires 222 via timer wires 216.

Typical heater 102 includes a gas supply 110, burner 116 producing a flame 118.

Certain components of heater 102 are not shown for simplicity sake for example, the mixing of air with gas supply 110 is not shown and also the ignition source for lighting flame 118 is also not shown. The components of heater 102 which interact with burner shut off 100 are generally shown namely burner 116 having flame 118 as well as solenoid valve 230.

In Use

Heater 102 is started in the manner generally known in the art namely, manual push button 232 of solenoid valve 230 is manually depressed in order to allow gas supply 110 to flow freely to burner 116. Not shown, gas is mixed in appropriate proportions with air in order to produce a combustible mixture of fuel and air which can be ignited at the end of burner 116 to produce flame 118. An ignition source not shown is used to ignite the combustible fuel mixture at the end of burner 116 to produce flame 118. Once flame 118 has been initiated, it heats thermocouple 220 and the heating of thermocouple 220 creates a millivolt output normally in the range between 0.007 to 0.020 volts (7 to 20 millivolts) and this potential produced by thermocouple 220 is electrically communicated back to solenoid 230. The millivolt out of thermocouple 220 is enough to hold the solenoid valve 230 in the open position allowing gas supply 110 to flow freely to burner 116.

A person skilled in the art will recognize that once thermocouple 220 has been heated to the normal operating temperature by flame 118, enough millivolts and/or current are produced by thermocouple 220 to hold solenoid valve 230 in the open position, and therefore manual push button 232 can be released and the valve 230 is retained in the open position to ensure continuous firing of burner 116.

Thermocouple 220 is there to ensure that should for some reason flame 118 be extinguished, thermocouple 220 will naturally cool down and therefore the millivolts produced by thermocouple 220 will decrease to a point where the current produced by thermocouple 220 can no longer hold solenoid valve 230 in the open position and therefore, gas supply 110 will be shut off. A person skilled in the art will recognize this as a normal safety feature that is found on many commercially available portable space heaters for safety purposes to ensure that the gas supply 110 is cut off should there be an interruption or an extinguishment of flame 118.

A person skilled in the art will recognize that the electromotive force or the voltage output of thermocouple 220 is extremely low, normally in the range of 7 to 20 millivolts and once the voltage falls below about 5 millivolts the solenoid valve 230 will normally trip to the closed position.

A person skilled in the art will also recognize that due to the small millivolt output of thermocouple 220, the electrical connections between thermocouple 220 and solenoid valve 230 are extremely sensitive, particularly to any contact resistance which may inhibit the flow of current between thermocouple 220 and solenoid valve 230 along thermocouple wires 222. Therefore, any mechanical contact which is introduced between thermocouple 220 and solenoid valve 230 may be undesirable in that it may introduce an unwanted contact resistance and falsely close solenoid valve 230 when in fact, flame 118 has not been extinguished.

Therefore in one embodiment a burner shut off 100 is contemplated which will allow solenoid valve 230 to shut gas supply 110 without introducing any mechanical contact resistance of additional switches or contacts along thermocouple wires 222. In other words thermocouple wires 222 are continuous and free of intervening contacts between thermocouple 220 and solenoid valve 230 in order to ensure the most reliable operation of heater 102. This continuous aspect of thermocouple wires 222 means there are no mechanical contacts introduced between thermocouple 220 and solenoid 230 other than to accomplish connection between thermocouple 222 and solenoid 230. The connection between the timer wires 216 and thermocouple wires 222 does not introduce a mechanical contact and therefore no additional contact resistance along thermocouple wires 222. The timer wires 216 are connected to the thermocouple wires using a contact less connection 219. The contact less connection can be in any location provided a connection is made to the solenoid 230. In another embodiment it is contemplated that contacts may be used provided the contact resistance does not falsely close solenoid valve 230.

One embodiment includes a safety timer 202 which consists of a circuit board 214 having thereon a timer 204 which is electronic in nature and furthermore includes a micro processor 206, and further includes a power storage device 208 and has a power supply which could be a battery 212. Circuit board 214 further includes a reset button 210 which is a manual push button or other type of button and/or switch device which upon pushing of the reset button 210 initiates the timer cycle which may for example be a preselected programmed amount of time through processor 206 and timer 204.

For example, heater 102 is ignited and lit in the conventional manner as described above by manually depressing manual push button 232 igniting flame 118, wherein thermocouple 220 is brought up to temperature and the solenoid valve 230 is held open by thermocouple 220 even after the release of manual push button 232. At this point in time, heater 102 will continue to operate until there is an interruption in the signals between thermocouple 220 and solenoid valve 230.

Initiating the current between thermocouple 220 and solenoid valve 230, acts to initiate the timer 204 of safety timer 202 which provides for a preset amount of time before an event is triggered by circuit board 214. So for example, by initiating firing of burner 116, namely flame 118, the heater 102 will operate for example for a period of 10 minutes as predetermined by microprocessor 206 and timer 204 after which time safety timer 202 will create a reverse bias electromotive force (millivolt signal) along timer wires 216 which effectively counteracts the millivolt output developed by thermocouple 220. In other words a voltage signal or electromotive force of about 20 millivolts (0.020 volts) will be created across thermocouple wires 212 in reverse polarity to the natural millivolt output of thermocouple 220, therefore the applied voltage at solenoid 230 will in effect be reduced to zero or very close to zero.

If in the above example, the operator presses reset button 210 prior to the expiry of the 10 minutes allotted by timer 204, timer 204 together with microprocessor 206 is reset to allow for an additional 10 minutes before an event is again triggered by safety timer 202.

Upon expiration of the next 10 minutes, safety timer 202 will automatically create a millivolt signal across timer wires 216 which counteract the millivolt signal created by thermocouple 220, therefore reducing the voltage seen by solenoid valve 230 effectively to zero, thereby causing gas supply 110 to be shut off.

Therefore, heater 102 is allowed to operate for a maximum time of 10 minutes unless resent button 210 is depressed prior to the expiration of the preset time of 10 minutes.

Should a heater 102 be used in a confined space, and the occupant for example become unconscious and unable to press reset button 210, heater 102 will automatically be shut down by safety timer 202, extinguishing flame 118 and shutting off gas supply 110.

If for some reason there is failure of the power supply, namely battery 212 to circuit board 214, safety timer 202 will detect this condition and there will be enough residual power stored within power storage 208 to be able to send enough electromotive force across timer wires 216 to counteract the millivolt output generated by thermocouple 220 and therefore shut down heater 102. The power storage 208 could be a capacitor or inductor or a combination of electrical components which are capable of storing enough residual power to produce the reverse polarity voltage signal to close solenoid valve 230.

The cycle time of timer 204 is preselected depending upon the application and can vary any where from a few seconds to many hours. It normally is a pre-programmed amount of time however could also be a selected value.

A person skilled in the art will immediately recognize that the advantages of having an electrical connection between thermocouple wires 212 and timer wires 216 which eliminates mechanical switch contacts used to break the connection between thermocouple 220 and solenoid valve 230. In one embodiment the electrical connection between thermocouple 220 and solenoid valve 230, namely thermocouple wires 222 are not mechanically broken to effect shut off. The shut off of solenoid valve 230 is accomplished by permanent electrical connections between timer wire 216 and thermocouple wires 222 by applying a reverse bias voltage to thermocouple wires 222.

In addition, the safety timer 202 can operate very easily with a portable battery power of for example three volts or less creating a safety timer not depending on 110 volt AC line current.

Additionally, this safety timer shut off device provides for a low cost method of efficiently shutting down heater 102 and a completely self contained apparatus not requiring any sources of external power other than the self contained battery 212.

It should be apparent to persons skilled in the arts that various modifications and adaptation of this structure described above are possible without departure from the spirit of the invention the scope of which defined in the appended claims. 

1. A burner shutoff for a portable heater comprising; (a) a burner including a solenoid moveable between an open position permitting fuel supply to the burner and a closed position cutting off fuel supply to the burner; (b) a thermocouple in communication with the solenoid, wherein the thermocouple producing a voltage output signal when heated by the burner for maintaining the solenoid in the open position; (c) a safety timer for selectively generating and communicating a reverse polarity voltage signal to the solenoid such that the voltage signal received by the solenoid is altered sufficiently to move the solenoid to the closed position, thereby shutting off the burner.
 2. The burner shutoff claimed in claim 1, wherein the safety timer including a timer for operably communicating the reverse polarity voltage signal at pre selected times.
 3. The burner shutoff claimed in claim 2 wherein the safety timer including a micro processor for initiating a pre selected timed interval thereby operably communicating the reverse polarity voltage signal at the end of the pre selected timed interval.
 4. The burner shutoff claimed in claim 3, wherein the safety timer including a self contained power supply.
 5. The burner shutoff claimed in claim 3, wherein the safety timer including a self contained power supply including a battery.
 6. The burner shutoff claimed in claim 4, wherein the safety timer including a power storage device which is activated upon failure of the self contained power supply and will provide enough power for operably communicating the reverse polarity voltage signal to the solenoid, thereby shutting off the burner.
 7. The burner shutoff claimed in claim 1, wherein the thermocouple connected to the solenoid with thermocouple wires.
 8. The burner shutoff claimed in claim 7, wherein thermocouple wires being continuous between the solenoid and thermocouple.
 9. The burner shutoff claimed in claim 8, wherein the safety timer connected to the thermocouple wires with timer wires at a contact less connection without introducing additional contact resistance along the thermocouple wires.
 10. A method of shutting off a burner, the method comprising: configuring a burner to comprise, a solenoid moveable between an open position permitting fuel supply to the burner and a closed position cutting off fuel supply to the burner, a thermocouple in communication with the solenoid, wherein the thermocouple producing a voltage output signal when heated by the burner for maintaining the solenoid in the open position; (a) igniting the burner, (b) generating a reverse polarity output signal, (c) communicating the reverse polarity voltage signal to the solenoid such that the voltage signal received by the solenoid is altered sufficiently to move the solenoid to the closed position, thereby shutting off the burner.
 11. The method claimed in claim 10 wherein step a) is as follows: (a) generating a reverse polarity output signal at a selected time controlled by a safety timer which is in communication with the solenoid.
 12. The method claimed in claim 11 wherein the safety timer including a self contained power supply.
 13. The method claimed in claim 11 wherein the thermocouple connected to the solenoid with thermocouple wires and the safety timer connected to the thermocouple wires with timer wires at a contact less connection without introducing additional contact resistance along the thermocouple wires.
 14. A system for shutting off a burner comprising; (a) a burner including a solenoid moveable between an open position permitting fuel supply to the burner and a closed position cutting off fuel supply to the burner; (b) a thermocouple in communication with the solenoid, wherein the thermocouple producing a voltage output signal when heated by the burner; wherein the voltage output signal received by the solenoid maintaining it in the open position; (c) a reset button for initiating a timer within a safety timer, the safety timer for generating and communicating a reverse polarity output signal to the solenoid such that the voltage signal received by the solenoid is altered sufficiently to move the solenoid to the closed position, thereby shutting off the burner.
 15. The system claimed in claim 14 wherein upon expiration of the timer the safety timer communicating the reverse polarity voltage signal to the solenoid.
 16. The system claimed in claim 15 wherein upon depressing the reset button prior to expiration of the timer resets the timer back to a pre determined value.
 17. The system claimed in claim 14 wherein the safety timer including a self contained power supply including a battery.
 18. The system claimed in claim 17 wherein the safety timer including a power storage device which is activated upon failure of the self contained power supply and will provide enough power for operably communicating the reverse polarity voltage signal to the solenoid, thereby shutting off the burner.
 19. The system claimed in claim 14 wherein the thermocouple connected to the solenoid with thermocouple wires.
 20. The system claimed in claim 19 wherein thermocouple wires being continuous between the solenoid and thermocouple.
 21. The system claimed in claim 20 wherein the safety timer connected to the thermocouple wires with timer wires at a contact less connection without introducing additional contact resistance along the thermocouple wires. 